Dangerous Roundabout

I have observed numerous near misses here over the years. One of my friend was actually hit side-on a few years back in this roundabout when the other drivers (entering a roundabout on our left) are supposed to give way. Many cars getting on the Ellerslie-Panmure Highway on-ramp from the Southbound direction does not appear to realise that they are entering a roundabout and cars already in the roundabout from the Northbound end has the right of way. This is somewhat understandable especially if they are not paying close attention to road signs, as the outermost left two Southbound lanes head straight onto the onramp without obvious road curvature to indicate they are going into a roundabout. This is not an issue during rush hour traffic as cars queue up here and hence forced to stop. When there are no traffic however, some cars go through this roundabout at speed. Many drivers just look straight ahead, do not even look to their right or slow down to give way. I have observed numerous cars in the roundabout having to slam on their brakes to prevent a crash (myself included). Council or the Police should observe this roundabout for a couple of days especially during quieter times to see what I mean. The only solution I could think of is the placement of speed bumps on the Southbound end just before the roundabout (between Sultan Street and the roundabout itself) to force cars to slow down which will hopefully make them more aware that they are entering a roundabout. Please see the attached diagram which demonstrate the issue I would like to raise - the red arrow represents the two lanes where cars are speeding through the roundabout without stopping. The blue arrows represent cars already in the roundabout who are at risk of being crashed into. Thank you for your help.